1. Field of the Invention
This invention pertains to an accumulator and charging unit interposed in the refrigerant conduit between the evaporator and the compressor of a vapor-compression refrigeration system to minimize liquid refrigerant ingestion into the compressor and to provide for rapid, visual and proper charging of the system with refrigerant fluid.
2. Background
A longstanding problem in the art of vapor-compression refrigeration systems pertains to proper charging of the system with the correct amount of refrigerant fluid. If a system is overcharged with fluid there is a tendency to flood the compressor with liquid refrigerant due to incomplete vaporization of the refrigerant fluid as it passes through the evaporator. Moreover, in systems which operate on a repeated on/off cycle it is common for liquid refrigerant to collect in the evaporator and compressor suction conduit, particularly, if the compressor is located at an elevation below the evaporator unit. Accordingly, upon start up of the compressor liquid is ingested into the compression chambers and serious damage to the compressor may be incurred. Therefore, it is desirable to place a pressure vessel in the refrigerant flow circuit between the evaporator and the compressor to provide for minimizing the tendency for liquid to be ingested into the compressor inlet during steady state operating conditions and particularly on start up of the compressor.
A related problem in the installation, servicing and operation of vapor-compression refrigeration systems pertains to the inability to accurately charge the system with the proper amount of refrigerant fluid for design load conditions to prevent refrigerant fluid from failing to evaporate in the evaporator section, which occurs if the system is overcharged, and on the other hand to minimize superheating the refrigerant fluid prior to compression as a result of a system being undercharged. In the former case, inefficient and potentially damaging operation of the system is incurred and, in the latter case, the system operates in an inefficient mode in that a less efficient compression process occurs with superheated refrigerant inlet fluid flowing to the compressor. Although pressure and temperature readings may be taken at various points in a vapor-compression-refrigerant system to ascertain if a proper charge of refrigerant fluid is present, such readings are subject to inaccuracies and in many installations are not conveniently obtainable.
The ideal vapor-compression refrigeration process includes isentropic compression of saturated vapor followed by a constant pressure condensing to saturated liquid, a constant enthalpy expansion and then a constant pressure evaporation process to produce saturated vapor. Although various system inefficiencies prevent the ideal process from occurring in practice an improved apparatus and method in accordance with the present invention provides for visual indication of the condition of the refrigerant fluid flowing through the conduit leading to the compressor inlet and adjustment of the quantity of refrigerant fluid in the system to provide the proper charge of fluid.